1. Field of the Invention
The present invention relates to a sliding device for the gas-tight and air-tight closure of a container opening of given size or of a conduit having a specific inner diameter. The device comprises a locking member which is displaceable by means of a push rod and which comprises a sealing plate having a counter element connected therewith by means of a spring member. In the locking member, spreading elements are provided which rest against the sealing plate and the counter element to spread them apart after the locking member has been moved into the closing position and to press the sealing plate onto a seat of the container or conduit in a seal-tight manner through the intermediary of a seat packing.
2. Description of the Prior Art
A frequent requirement of shutoff sliding devices is that they can be mounted in the conduit as required without regard to the direction of flow. This requirement presupposes that the seal-tightness at the sealing plate or valve plate remains unchanged regardless of which side of the plate is exposed to overpressure or thrust pressure as a result of the blocked flow.
If the shutoff sliding device is mounted in the conduit in such a way that the overpressure presses the valve plate-and thus the packing-onto the valve seat, the sealing pressure is additive to the pressure and thus, with increasing overpressure, the seal-tightness is increased. However, if the shutoff sliding device is mounted in the conduit in such a way that the overpressure produced at the closed valve plate is effective in the opposite direction to the sealing force, the latter is reduced by the overpressure and constructional measures must be adopted which are so costly, particularly in the case of large shutoff sliding devices, that in most cases it is not possible to meet the requirement--which is feasible as such -- of providing seal tightness in each direction in the case of overpressure.
This restriction is applicable, in particular, to all shutoff sliding devices, as must have a very high degree of seal-tightness which is essential in the case of high vacuum sliding devices. It also applies to the shutoff sliding devices disclosed in U.S. Pat. No. 3,368,792. In the case of the shutoff sliding devices described in the afore-mentioned patents, the locking member comprises as its spreading elements at least one pair of bearings which are loosely inserted one above the other in an appropriate continuous bore in the locking member. The combined diameter of the two bearings is greater than the length of the bore and the valve plate, and a counter plate comprises oppositely disposed recesses in which the bearings are inserted in the opening position of the locking member and which the bearings are forced to vacate by the closing movement of the push rod, thereby spreading apart the plates when the valve plate is disposed opposite its seat.
The same difficulties also arise in the case of a sliding device of the type described initially when it is intended for use as a gas-tight and air-tight closure of a container, more particularly, as the doors of a pressure capsule, for example, in connection with training and test capsules and annexed lock chambers for astronautical projects. In the case of systems of this type, the overpressure may occur alternately on either side of the locking doors, and thus it is necessary to provide expensive reinforcement devices such as clamps with spindles for occasions when the overpressure exerted on the closed sealing plate is effective in the opposite direction to the sealing force.
However, devices of the above type are not only undesirable because they are very expensive but, above all, because the operation of these devices is time consuming. In the case of astronautical test capsules it is essential that in an emergency, for example, in the event of damage to the pressure suit of the person undergoing the test in the pressure capsule, that the access door can be opened within a very few seconds. This is impossible when additional reinforcing devices have to be provided.